Because a group of changelings working a menial 9-5 job in a ketracel white factory would be beneath them when they can be doing important things like oozing out.

So being wiped out by their own soliders is preferable to that? I can't believe you'd even suggest such a thing.

--Sran

Your belief seems to be rather constrained. They have a vast interplanetary empire that dwarfs the Federation. There are other safeguards than for the ruling class to work in the factories themselves. Have secret factories with Vorta in them. Vorta are equipped with suicide implants. A self destruct just in case rogue Jem'Hadar both find and attack the factory isn't out of the question.

Or have loyal client races manufacture the individual components, then bring them to a classified area for the yet another race to assemble the drug. All of them being in the dark. The Founders trust them enough to distribute the drug after all. Unless you think a Founder individually hands out each tube to each soldier, which we've seen isn't true. We've seen that the client races, such as the Karemma, are trusted with manufacture of weapons after all.

The Founders are elitist(yes elitist is the most polite word for a group of people who believe in their racial superiority and think that everything related to the solids is beneath them) jerks, but they're not stupid. That's why they have the genetic coding -and- the white. Redundancy. I'm sure they applied the same concept to the varying degrees to the means in which they employ that control.